The present invention relates to the art of nuclear medicine, and particularly to the art of positron coincidence detection (PCD).
Positron emission tomography (PET) is a branch of nuclear medicine in which a positron-emitting radiopharmaceutical such as .sup.18 F-fluorodeoxyglucose (FDG) is introduced into the body of a patient. Each emitted positron reacts with an electron in what is known as an annihilation event, thereby generating a coincident pair of 511 keV gamma rays which travel in opposite directions along what is known as a line of coincidence. The coincident pair is detected and used to create a clinically useful image.
Traditionally, PET scanners have used detector elements arranged in circles or rings about the imaging region, with a plane of the rings perpendicular to the axis of the imaging region. Each ring corresponds to an axial slice of the patient. Data from each ring of a plurality of slices is reconstructed using a two or three dimensional reconstruction algorithms to create images of the patient.
The demand for PET has been steadily increasing. The positron emitting pharmaceutical FDG may be the most important nuclear imaging agent to date because of its ability to tag malignant tumors. It is highly desirable to screen patients from head to toe or toe to head for suspected tumors using FDG prior to performing more localized PET or other imaging techniques. However, the potential of PET imaging as a general screening tool cannot be fully realized because conventional PET imaging systems have a small axial field of view (generally less than 150 mm) and are very expensive (ranging from $1.2 to $2.9 million).
The development of large field of view multiple head gamma detector systems capable of performing positron coincidence imaging offers a more cost effective alternative to conventional PET imaging systems. This invention addresses the practical implementation of whole body PET imaging using large field of view gamma detector systems.